Aircraft may be broadly classified into fixed wing and rotating wing types. Fixed wing aircraft typically include a plurality of flight control surfaces that, when controllably positioned, guide the movement of the aircraft from one destination to another. The number and type of flight control surfaces included in an aircraft may vary, but typically include both primary flight control surfaces and secondary flight control surfaces. The primary flight control surfaces are those that are used to control aircraft movement in the pitch, yaw, and roll axes, and the secondary flight control surfaces are those that are used to influence the lift or drag (or both) of the aircraft. Although some aircraft may include additional control surfaces, the primary flight control surfaces typically include a pair of elevators, a rudder, and a pair of ailerons, and the secondary flight control surfaces typically include a plurality of flaps, slats, and spoilers. Rotating wing aircraft typically do not have flight control surfaces that are separate from the airfoils that produce lift, but the airfoils that constitute the rotating wing have a cyclic control for pitch and roll, and a collective control for lift.
The positions of the aircraft flight control surfaces are typically controlled using a flight control surface actuation system. The flight control surface actuation system, in response to position commands that originate from either the flight crew or an aircraft autopilot, moves the aircraft flight control surfaces to the commanded positions. In most instances, this movement is effected via actuators that are coupled to the flight control surfaces. Typically, the position commands that originate from the flight crew are supplied via one or more user interfaces. For example, many aircraft include duplicate mechanical interfaces, such as yokes and pedals, one set each for the pilot and for the co-pilot. Either of the mechanical pilot or co-pilot user interfaces can be used to generate desired flight control surface position commands.
Recently, the mechanical user interfaces are being replaced with active fly-by-wire user interfaces in many aircraft. Similar to the traditional mechanical user interfaces, it is common to include multiple active user interfaces in the cockpit, one for the pilot and one for the co-pilot. In some implementations, one or more orthogonally arranged springs are used to provide a passive centering force to the fly-by-wire user interfaces. In other implementations, one or more electric motors supply force feedback (or “haptic feedback”) to the user, be it the pilot or the co-pilot. These latter implementations are generally referred to as active user interface haptic feedback systems.
No matter the specific type of user interfaces that are used, it is desirable in active user interface haptic feedback systems that the pilot and co-pilot user interfaces be linked. That is, that the movements of the corresponding pilot and co-pilot user interfaces track each other. This, among other things, assures that only a single set of position commands is supplied to the flight control surface actuation system, and that the pilot and co-pilot feel each other's influence on their respective user interfaces.
Most active user interface haptic feedback systems implement pilot and co-pilot linking using force information supplied from force sensors associated with the pilot and co-pilot user interfaces. The force sensors that are typically used are relatively high-fidelity force sensors, which increase overall system cost and complexity. Moreover, when redundancy is employed to increase overall system reliability, the increased cost and complexity can be significant.
Hence, there is a need for an active user interface haptic feedback system for aircraft that provides pilot and co-pilot linking and that exhibits suitable fidelity and/or redundancy, without significantly impacting overall system cost and complexity. The present invention addresses at least this need.